Not applicable.
Not applicable.
Electronic grade metal oxides and oxynitrides have found increasing interest as dielectric films in microelectronic devices. For instance, tantalum oxide (Ta2O5) has a high dielectric constant (k=22) and is considered a promising material for applications in microelectronics devices as a gate oxide and as a DRAM storage capacitor. For example, Treichel et al. Adv. Mat. Opt. Elec. 1992, 1, p.299-308. As the size of integrated circuit devices become increasingly smaller, chemical vapor deposition (CVD) shows a unique advantage over physical vapor deposition (PVD) for device fabrication in terms of excellent step coverage for trench and stack cell structures. For the CVD processing of Ta2O5 thin films, various precursors have been studied thus far. A liquid precursor is desirable for the ease and reproducibility of precursor delivery. Tantalum halides (TaX5, Xxe2x95x90F, Cl), Devine, R. A. B. et al. Appl. Phys. Lett. 1996, 68, p.1775-1777, Devine, R. A. B. et al. Microelec. Eng. 1997, 36, p.61-64, Jeon, S. R. et al. J. Appl. Phys. 1995, 77, p.5978-5981, suffer from low volatility and difficulty in delivery due to their solid nature. A solid amide complex Ta(NMe2)5 (pentakis(dimethylamino)tantalum) has been reported to provide Ta2O5 films by CVD. Tabuchi, T. et al. Jap. J. Appl. Phys. 1991, 30, p.L1974-1977. These films, however, contain significant impurities such as carbon and nitrogen. The most commonly studied alkoxide complex Ta(OEt)5 (tantalum pentaethoxide), Laviale, D. Appl. Phys. Lett. 1994, 65, p.2021-2023, Nagahori et al. J. Am. Ceram. Soc. 1995, 78, p.1585-92, Kim, I. et al. J. Mat. Res. Soc. 1995, 10, p.2864-2869, Aoyama, T. et al. J. Electrochem. Soc. 1996, 143, p.977-983, is a liquid and has a marginal vapor pressure for CVD applications, and the resulting films contain carbon impurities. Therefore, an alternative liquid precursor which has sufficient volatility and capability to afford pure Ta2O5 is of keen interest.
U.S. Pat. No. 5,677,015 discloses the preparation of tantalum oxynitride materials from a precursor of CpmTa(N3)n where Cp is cyclopentadienyl. The reaction can be thermal or plasma CVD. Ammonia, oxygen, ozone, nitrous oxide, hydrazine are used in the reaction. No physical characteristics of the precursors are described in the patent.
U.S. Pat. No. 5,248,629 discloses the preparation of TaOxNy films from the reaction of Ta[N(R)2]5 such as Ta[N(CH3)2]5 and Ta(OCH3)5. Ta[N(CH3)2]5 and Ta(OCH3)5 are both solid at room temperature.
Reactions of various tantalum sources containing alkylamide ligands to produce tantalum nitride or carbonitride are disclosed in Fix, et. al., Chemical Vapor Deposition of Vanadium, Niobium and Tantalum Nitride Thin Films, Chem. Mater., Vol. 5, (1993) pp. 614-619; Tsai, et. al., Metalorganic Chemical Vapor Deposition Of Tantalum Nitride By Tertbutylimidotris(Diethylamido)Tantalum For Advanced Metallization, Appl. Phys. Lett. 67, (8) August 1995, pp. 1128-1130; Chiu, et. al., Syntheses and Characterization of Organoimido Complexes of Tantalum; Potential Single-Source Precursors to Tantalum Nitride, Polyhedran, Vol. 17, Nos. 13-14, (1998) pp. 2187-2190; and Chiu, et. al., Deposition of Tantalum Nitride Thin Films From Ethylimidotantalum Complex, J. Mat. Sci. Lett, Vol. 11, (1992) pp. 96-98. The latter article indicates that some authors have misidentified Ta(NCH2CH3)5, when in fact they were using a combination of [(CH3CH2)2N]3Taxe2x95x90NCH2CH3 and [(CH3CH2)2N]3Ta[xcex72xe2x80x94CH3CH2Nxe2x95x90CH(CH3)]. Jun et. al., Low Temperature Deposition of TaCN Films Using Pentakis(diethylamido)tantalum, Jpn. J. Appl. Phys. , Vol. 37, (1998), pp.L30-L32, discloses the deposition of the name compounds.
EP 0 869 544 A2 describes the reaction of [(CH3CH2)2N]3Taxe2x95x90NCH2CH3 with ammonia to form tantalum nitride.
Chiu, et. al., Deposition of Molybdenum Carbonitride Thin Films From Mo(NBut)2(NHBut)2, J. Mater. Res., Vol. 9, No. 7, (July 1994), pp.1622-1624, describes the CVD deposition of molybdenum carbonitride compounds from the title precursor.
Chiu, et. al., Tungsten Nitride Thin Films Prepared by MOCVD, J. Mater. Res., Vol. 8, No. 6, (June 1993), pp.1353-1360, describes the MOCVD deposition of tungsten nitride compounds from W(NBut)2(NHBut)2.
Chiu, et. al., Syntheses and Characterization of Organoimido Complexes of Niobium(V); Potential CVD Precursors, J. Chin. Chem. Soc., Vol. 45, No. 3, (1998), pp. 355-360, describes the multi-step synthesis of (RN)Nb(NEt2)3 without formation of the cyclic precursor structure typified in the tantalum analog. The niobium compounds are reported to be useful for metal nitrides and carbonitrides.
The problems of the prior art have been overcome by the present invention, by providing an appropriate liquid precursor with an attractive vapor pressure for chemical vapor deposition of tantalum, niobium, molybdenum and tungsten oxide and oxynitride in a thermal process as will be set forth in greater detail below.
The present invention is a method for producing a material selected from the group consisting of a metal oxide, metal oxynitride and mixtures thereof, wherein the metal is tantalum, niobium, molybdenum or tungsten, on a substrate, comprising; reacting a first reactant selected from the group consisting of (R1R2N)xM(xe2x95x90NR3)y, (R4R5N)xM[xcex72xe2x80x94R6Nxe2x95x90C(R7)(R8)]y and mixtures thereof with an oxidant and up to 95 volume percent of a source of nitrogen selected from the group consisting of ammonia, N2 O, NO, NO2, alkyl amines, N2H2, alkyl hydrazine, N2 and mixtures thereof, to produce the material on the substrate, where R1, R2, R3, R4, R5, R6, R7 and R8 are individually C1-6 alkyl, aryl or hydrogen, M Ta, Nb, W, Mo or mixtures thereof, and when Mxe2x95x90Ta or Nb, x=3 and y=1 and when Mxe2x95x90W or Mo, y=x=2.
Preferably, the oxidant is selected from the group consisting of oxygen, ozone, water, hydrogen peroxide, nitrous oxide and mixtures thereof.
Preferably, the material is tantalum oxide.
Alternatively, the material is tantalum oxynitride.
Preferably, the first reactant is selected from the group consisting of [(CH3CH2)2N]3Taxe2x95x90NCH2CH3, [(CH3CH2)2N]3Ta[xcex72xe2x80x94CH3CH2Nxe2x95x90CH(CH3)] and mixtures thereof.
Preferably, the pressure is in the range of 1 mTorr to 760 Torr, more preferably 0.5 to 1.5 Torr.
Preferably, the temperature is in the range of 200xc2x0 C. to 600xc2x0 C., more preferably 280xc2x0 C. to 400xc2x0 C.
Preferably, the substrate is silicon.
Preferably, the precursor vaporization temperature is in the range of 50xc2x0 C. to 150xc2x0 C., more preferably 85xc2x0 C. to 100xc2x0 C.
More specifically, the present invention is a chemical vapor deposition method for producing a material selected from the group consisting of tantalum oxide, tantalum oxynitride and mixtures thereof on a silicon substrate comprising reacting a first reactant selected from the group consisting of [(CH3CH2)2N]3Taxe2x95x90NCH2CH3, [(CH3CH2)2N]3Ta[xcex72xe2x80x94CH3CH2Nxe2x95x90CH(CH3)] and mixtures thereof with an oxidant selected from the group consisting of oxygen, ozone, hydrogen peroxide, water, nitrous oxide and mixtures thereof and up to 95 volume percent of a source of nitrogen selected from the group consisting of ammonia, N2O, NO, NO2, alkyl amines, N2H2, alkyl hydrazine, N2, and mixtures thereof, to produce the material on the silicon substrate.
Alternatively, more specifically, the present invention is a chemical vapor deposition method for producing tantalum oxide on a silicon substrate comprising reacting a first reactant selected from the group consisting of [(CH3CH2)2N]3Taxe2x95x90NCH2CH3, [(CH3CH2)2N]3Ta[xcex72xe2x80x94CH3CH2Nxe2x95x90CH(CH3)] and mixtures thereof with an oxidant selected from the group consisting of oxygen, ozone, hydrogen peroxide, water, nitrous oxide and mixtures thereof to produce the tantalum oxide on the silicon substrate.
Alternatively, the present invention is a chemical vapor deposition method for producing a material selected from the group consisting of tungsten oxide, tungsten oxynitride and mixtures thereof on a silicon substrate comprising reacting a first reactant selected from the group consisting of [(CH3CH2)2N]2W(xe2x95x90NCH2CH3)2, [(CH3CH2)2N]2W[xcex72xe2x80x94CH3CH2Nxe2x95x90CH(CH3)]2 and mixtures thereof with an oxidant selected from the group consisting of oxygen, ozone, hydrogen peroxide, water, nitrous oxide and mixtures thereof and up to 95 volume percent of a source of nitrogen selected from the group consisting of ammonia, N2O NO, NO2, alkyl amines, N2H2, alkyl hydrazine, N2 and mixtures thereof, to produce said material on said silicon substrate.
Further, alternatively, the present invention is a chemical vapor deposition method for producing a material selected from the group consisting of molybdenum oxide, molybdenum oxynitride and mixtures thereof on a silicon substrate comprising reacting a first reactant selected from the group consisting of [(CH3CH2)2N]2Mo(xe2x95x90NCH2CH3)2, [(CH3CH2)2N]2Mo[xcex72xe2x80x94CH3CH2Nxe2x95x90CH(CH3)]2 and mixtures thereof with an oxidant selected from the group consisting of oxygen, ozone, hydrogen peroxide, water, nitrous oxide and mixtures thereof and up to 95 volume percent of a source of nitrogen selected from the group consisting of ammonia, N2O, NO, NO2, alkyl amines, N2H2, alkyl hydrazine, N2 and mixtures thereof, to produce said material on said silicon substrate.
Alternatively, the present invention is a chemical vapor deposition method for producing a material selected from the group consisting of niobium oxide, niobium oxynitride and mixtures thereof on a silicon substrate comprising reacting a first reactant selected from the group consisting of [(CH3CH2)2N]3Nbxe2x95x90NCH2CH3, [(CH3CH2)2N]3Nb[xcex72xe2x80x94CH3CH2Nxe2x95x90CH(CH3)] and mixtures thereof with an oxidant selected from the group consisting of oxygen, ozone, water, nitrous oxide and mixtures thereof and up to 95 volume percent of a source of nitrogen selected from the group consisting of ammonia, N2O, NO, NO2, alkyl amines, N2H2, alkyl hydrazine, N2 and mixtures thereof, to produce said material on said silicon substrate.
The present invention is also a method for producing a mixed metal compound on a substrate comprising: (1) a material selected from the group consisting of a metal oxide, metal oxynitride and mixtures thereof, wherein the metal is tantalum, niobium, molybdenum or tungsten, formed by reacting a first reactant selected from the group consisting of (R1R2N)xM(xe2x95x90NR3)y, (R4R5N)xM[xcex72xe2x80x94R6Nxe2x95x90C (R7)(R8)]y and mixtures thereof with an oxidant and up to 95 volume percent of a source of nitrogen selected from the group consisting of ammonia, N2O , NO, NO2, alkyl amines, N2H2, alkyl hydrazine, N2 and mixtures thereof, to produce said material on said substrate, where R1, R2, R3, R4, R5, R6, R7 and R8 are individually C1-6 alkyl, aryl or hydrogen, Mxe2x95x90Ta, Nb, W, Mo or mixtures thereof, and when Mxe2x95x90Ta or Nb, x=3 and y=1 and when Mxe2x95x90W or Mo, y=x=2; and (2) one or more additional metals or metal compounds other than tantalum, niobium, molybdenum or tungsten formed by decomposing a precursor of such one or more additional metals on the substrate.
Preferably, the precursor of the additional metal is selected from the group consisting of metal alkyls, metal alkoxides, metal halides, metal hydrides, metal amides, metal azides, metal cyclopentadienyls, metal carbonyls, metal xcex2-diketonates metal xcex2-ketoiminates, metal xcex2-diiminates, and their fluorine substituted analogs and mixtures thereof.
More preferably, the precursor of the additional metal is co-deposited with the first reactant.